The first thing to do is look at it, and find out what "kind" of sand it is. The most common sands are calcium-type (limestone or coral, usually for saltwater tanks or cichlid tanks), quartz or silica type (this is also the most common sandbox/pool filter sand). A calcium-type sand is totally inappropriate for a community tank, as it has a heavy influence on Ph and dissolved minerals in the water, so skip that. If it's a silica-type sand, it may be OK.The only sand my lfs sells is river sand is this alright for cories?